1. Field of the Invention
This invention relates to novel desmosine derivatives and their application.
2. Description of the Prior Art
In the lungs, a balance is preserved between the elastase, one of the proteases and antielastase. Namely, as can be inferred the network of the elastic fibers of the lungs is protected by the action of the antielastase from the damages arising from its extension. When the balance is destroyed due to some cause, the elastin (elastic fibers), the main component of the lungs, undergoes an unlimited decomposition, resulting in the destruction of pulmonary cells and consequently chronic obstructive pulmonary disease (COPD). If a highly sensitive chemical analytic process is available which can determine the manner in which elastin is decomposed in the living organism, it will be possible to effectively detect changes in the morbid condition of various tissues and organs including the lungs as early as possible. When decomposed, elastin is excreted into the urine in the form of peptide containing cross-linked amino acid such as unique desmosine found in elastin alone. Consequently analysis of a quantity of desmosine excreted into the urine will ensure the discovery of the occurrence of pulmonary diseases.
Recently Harel et al, Am. Rev. Respir. Dis., Vol 122, p 769, 1980, and King et al Connect. Tissue Res., Vol 7, P 263, 1980 disclosed the process of analyzing desmosine contained in the urine by means of radioimmunoassay (RIA). However, since RIA method involves the use of radioisotopes, it presents various difficulties such as not only hazards to the human body, but also environmental pollution, difficulties in waste disposed, establishment of an extra facility required for the application of radioisotopes, and problems concerning the application period of radioisotopes due to their half-life. Consequently the RIA method involves numerous difficulties in being accepted as a general analytic method and is obstructed in rapid dissemination. Moreover, the artificial desmosine antigen developed by Harel et al or King et al is prepared by combining desmosine and protein at random using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride. Therefore, the artificial desmosine antigen proposed by the above-mentioned researchers gives an antibody having only an extremely low titer. Their analytic method only has the maximum merit of diluting antiserum to the extent of 200 to 250 times magnification. In this respect, too, the RIA method presents great difficulties in wide dissemination.
In view of the above-mentioned difficulties, it has become necessary to develop a new desmosine-analyzing method based on the enzymeimmunoassay (EIA). The EIA offers the advantages that less hazards are presented to the human body than RIA process when a clinical chemical examination is performed; difficulties are eliminated in dumping waste leading to environmental pollution; it is unnecessary to provide any extra facility for its application; reagents involved can be safely stored over a long period time; and wide dissemination is ensured.
Nevertheless, the EIA process is generally considered to have such an unsatisfactory detection sensitivity as is ten times lower than the RIA process. Therefore, antiserum applied to the EIA process is demanded to have an extremely high antibody titer.